In steel production, electric furnaces are presently used for the smelting of scrap iron. Such a furnace comprises a vessel in which electrodes penetrate and the base of which forms a hearth covered with refractory material and forming a basin in which the liquid steel obtained by smelting of the scrap iron accumulates. This steel must be discharged periodically into a transfer ladle by means of a horizontal spout which is an integral part of the hearth of the furnace and the base of which is equipped with a pouring orifice, having a substantially vertical axis, beneath which is placed the transfer ladle for the liquid steel. Generally, steel is poured out of the furnace by tilting the vessel.
The pouring orifice must be equipped with a removable closure device generally comprising a plate, which may be protected by a refractory material, forming a flap mounted so as to slide or tilt so that it may be applied on a seating arranged on the periphery of the discharge orifice of the pouring hole. Normally, the closure flap is covered, before the arrival of the liquid metal, with a protective powder filling the pouring hole.
The normal procedure for pouring is therefore as follows:
After smelting the scrap iron and filling the vessel, the steel covers the pouring hole or is drawn into the spout, e.g., by tilting the vessel. The pouring hole is then opened by sliding or tilting the closure flap and, after discharge by means of gravity of the protective powder contained in the pouring hole, pouring of the steel takes place.
When the desired mass of steel has run into the ladle, the container is caused to tilt in the opposite direction to discharge the liquid steel from the area located above the pouring hole, so as to stop the pouring. At this moment, the pouring hole ought to be closed by means of the flap. However, during pouring, a residue consisting of a solidified skin of steel having a cylindrical shape has formed on the periphery of the orifice, extending the pouring hole over a certain height. This residue prevents the flap being applied against its seating in a leakproof manner and must therefore be removed before closure of the flap. For this reason, when the container is tilted to discharge the steel from the area located above the pouring hole, it is necessary to manually clean the lower surface of the pouring hole in order to ensure correct application of the flap. The latter is then maneuvered so as to close the pouring hole and protective powder is then placed above the flap in the pouring hole, the container can then return to its normal working position, the pouring hole once again being covered with liquid metal for moving onto a new pouring.
Manual cleaning of the lower surface of the pouring hole is a difficult operation in a dangerous and inaccessible area and requires means of access such as a retractable platform in order to reach the pouring hole. For cleaning, use is made of a heavy and cumbersome tool which is difficult to handle and inaccurate, and this results in the risk of a false maneuver which can cause incorrect cleaning and local damage, with the risks of perforation and leakage of liquid steel during the smelting operation if the flap is badly applied on its seating.